Engineering Commons^™

Laser Intensity Scaling Through Stimulated Scattering In Optical Fibers, Timothy H. Russell

Theses and Dissertations

The influence of stimulated scattering on laser intensity in fiber optic waveguides is examined. Stimulated Brillouin scattering (SBS) in long, multimode optical waveguides is found to generate a Stokes beam that propagates in the fiber LP01 mode. Additionally, the same process is found to combine multiple laser beams into a single spatially coherent source. Limitations in beam cleanup and combining are also investigated to identify ways to overcome them. The last portion of the dissertation theoretically examines suppression of stimulated Raman scattering in fibers to eliminate the restriction this imposes on the power of a fiber laser or amplifier. The …

Air Vehicle Path Planning, Jeffrey M. Hebert

Theses and Dissertations

This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An analytic solution yielding the trajectory minimizing the received radar energy reflected from the target is derived using the Calculus of Variations. Additionally, the related problem of an air vehicle tracked by a passive sensor is also solved. Using the insights gained from the single air vehicle radar exposure minimization problem, a hierarchical cooperative control law is formulated to determine the optimal trajectories that …

Nonlinear Suppression Of Range Ambiguity In Pulse Doppler Radar, Jon M. Anderson

Theses and Dissertations

Coherent pulse train processing is most commonly used in airborne pulse Doppler radar, achieving adequate transmitter/receiver isolation and excellent resolution properties while inherently inducing ambiguities in Doppler and range. First introduced by Palermo in 1962 using two conjugate LFM pulses, the primary nonlinear suppression objective involves reducing range ambiguity, given the waveform is nominally unambiguous in Doppler, by using interpulse and intrapulse coding (pulse compression) to discriminate received ambiguous pulse responses. By introducing a nonlinear operation on compressed (undesired) pulse responses within individual channels, ambiguous energy levels are reduced in channel outputs. This research expands the NLS concept using discrete …

Reduced Order Modeling For High Speed Flows With Moving Shocks, David J. Lucia

Theses and Dissertations

The use of Proper Orthogonal Decomposition (POD) for reduced order modeling (ROM) of fluid problems is extended to high-speed compressible fluid flows. The challenge in using POD for high-speed flows is presented by the presence of moving discontinuities in the flow field. To overcome these difficulties, a domain decomposition approach is developed that isolates the region containing the moving shock wave for special treatment. The domain decomposition implementation produces internal boundaries between the various domain sections. The domains are linked using optimization-based solvers which employ constraints to ensure smoothness in overlapping portions of the internal boundary. This approach is applied …

Automated Fault Detection In An Upflow Anaerobic Sludge Blanket Reactor: Comparisons Of Biogas Production And Physicochemical Quantities, Alexandra Maria Almeida Carvalho Pinto

Doctoral Dissertations

A system capable of rapidly detecting toxic loads entering high-rate anaerobic reactors would greatly enhance their reliability, and could thereby increase their commercial acceptance. A high-rate anaerobic wastewater treatment process, called the failure-causing load detector (FCLD), consisting of a small (4-liter) upflow anaerobic sludge blanket (UASB) reactor having a short (10-min) hydraulic retention time (HRT), was used as a biosensor to rapidly detect potential problems with the influent wastewater. Sensors were used to monitor biogas production in the reactor, as well as pH, conductivity, and turbidity in the effluent from the reactor. The FCLD system was tested using the following …

Acoustic Emission For Periodic Inspection Of Composite Pressure Vessels, Bao Rasebolai Mosinyi

Master's Theses - Daytona Beach

Cost savings can be achieved in a wide range of applications by replacing the current procedure for hydrostatic recertification of high-pressure composite gas cylinders with acoustic emission (AE) nondestructive testing. Advantages of AE recertification over the current hydrostatic method include: (1) no water contamination, since pressurization of the cylinders is done with air as opposed to water; (2) the risk of damage is decreased since the test pressure is reduced from 166% of design pressure to 110% of operating pressure; (3) the ability of acoustic emission to detect and locate flaws increases safety; and (4) the in-situ method will reduce …

Development Of A Model For Predicting The Vertical Profile Of Ozone Based On Ground-Level Ozone Observations And Cloud Cover, Gi-Dong Kim

Doctoral Dissertations

Ozone formed in a chemical reaction is vertically dispersed and mixed with the ozone mass aloft by turbulent convection due to solar radiation. The mixing height, which depends on the stability of the atmosphere, varies by day/night time and by season of year and is characteristic of season and day and night time from year to year. Ground level ozone is generally the combined result of dynamics of the atmosphere resulted from the turbulent convection in the atmospheric boundary layer (ABL), production and destruction processes such as transport from upper air mass, subsequent transport to the ground, photochemical production and …

Evaluation Of Poroton Masonry And Suggestion For Quick Design Procedure, Michael R. Radcliffe

Masters Theses

Poroton masonry units are highly cored extruded clay units with numerous thin webs. They have ground surfaces and are laid on a thin fluid mortar bed, with no mortar in the head joints. They offer the advantages of quick construction, which can be performed by a general labor force.

This thesis describes the results of component and prism testing of Poroton masonry. Compressive strength tests occurred on individual units and on prisms constructed with two units in accordance with the manufacturer’s directions. The average unit compressive strength was approximately 2900 psi. The average prism compressive strength was about 900 psi. …

A Molecular Investigation Of Absorption Onto Mineral Pigments, Brian J. Ninness

Electronic Theses and Dissertations

Pigment suspensions are important in several processes such as ceramics, paints, inks, and coatings. In the wet state, pigments are combined with a variety of chemical species such as polymers, surfactants, and polyelectrolytes which produce a complex colloidal system. The adsorption, desorption, and redistribution of these species at the pigment - aqueous solution interface can have an impact on the behavior in both the wet state or its final dried state. The goal of this work is to establish a molecular picture of the adsorption properties of these pigmented systems. A novel in situ infrared technique has been developed which …

The Relationship Between Rheology, Application Method, And Final Coating Structure, Basant Galal Dimetry

Electronic Theses and Dissertations

Paper is coated to improve the printability and the visual properties. The factors that determine the coating structure are important because the structure determines the physical, optical, and printing properties. This work focuses on determining a relationship between the rheological properties of the coating, the application method, and the final coating structure. Coatings with different polymers and pigments were characterized in terms of steady shear and viscoelastic properties. These coatings were applied onto plastic film and paper with a laboratory rod coater, a spray coater, and a high-speed blade coater. The final coating structure after drying was characterized in terms …

The Effects Of Dissolved Oxygen Concentration And Biological Solids Retention Time On Activated Sludge Treatment Performance, Jack Joseph Parker

Masters Theses

A bench scale treatment system with dissolved oxygen (DO) control was used to determine the effects of DO concentration and biological solids retention time (BSRT) on treatment performance using the activated sludge process. The four reactors, operating at BSRTs of 20, 10, 5, and 2 days, were fed settled municipal wastewater collected from the Kuwahee wastewater treatment plant in Knoxville, TN. The DO was maintained at different set points in each reactor ranging from 4.0 to 0.2 mg/L.

Experimental results indicate that carbon treatment performance improved, on average, with increasing BSRT but DO had little effect on carbon oxidation. Sludge …

A Computer Vision System For The Automatic Inspection Of Geometric Distortions In Television Displays, Geoffrey C. Yerem

Masters Theses

The ability to automatically measure the image quality of a television display is a valuable resource. In display manufacturing, automatic inspection enables automatic television alignment, which reduces manufacturing costs and improves product quality. Automatic inspection also comes in handy during competitive analysis and engineering review. Primarily though, commercial inspection systems are built and used for manufacturing.

In the past two decades, the advent of microcomputers has made automatic inspection feasible through the use of computer vision. Most of the approaches developed can be divided into two groups: fixtured systems, with fixed or movable cameras, and position independent systems, which …

Characterization Of Chitosan Films For Cell Culture Applications, Michael Katalinich

Electronic Theses and Dissertations

Chitosan (β-(l,4)-2-amino-2-deoxy-D-glucose) is a naturally occurring, abundant biopolymer exhibiting desirable biomaterial properties of biodegradability, low toxicity and good biocompatibility. These properties indicate the suitability of chitosan as a surface for mammalian cell growth. The goal of this thesis is to explore the potential for using chitosan as a surface for NIH 3T3 fibroblast attachment and growth. '4 standard, reproducible film-formation technique, based on other researchers techniques was established. The reproducibility of this technique. through characterization of the physical and chemical properties of these films, was good. The attachment and growth of NIH 3T3 fibroblasts on chitosan films and controls was …

Structural Studies Of Metastable Nanocrystalline Magnesium Titanate Ceramics, Renmei Xu

Masters Theses

Nanocrystalline magnesium titanate powders were produced using alkoxides of magnesium and titanium for the sol-gel method. High temperature phases which can only be formed at above 1200°C in equilibrium were formed at much lower temperature 600°C in nanometric system. Cation ordering and structural changes in qandilite (Mg₂TiO₄ ), geikielite (MgTiO₃ ) and karrooite (MgTi₂O₅ ) were studied by Rietveld refinement of neutron powder diffraction data and X-ray photoelectron spectroscopy. Single qandilite phases were obtained in a wide range of Mg:Ti ratios from 2:038:1 to 1.52:1, and appeared to be Mg_2-xTi_{1+x …}

Hierarchical Image Segmentation Using The Watershed Algorithim With A Streaming Implementation, Annapoorani Gothandaraman

Masters Theses

We have implemented a graphical user interface (GUI) based semi-automatic hierarchical segmentation scheme, which works in three stages. In the first stage, we process the original image by filtering and threshold the gradient to reduce the level of noise. In the second stage, we compute the watershed segmentation of the image using the rainfalling simulation approach. In the third stage, we apply two region merging schemes, namely implicit region merging and seeded region merging, to the result of the watershed algorithm. Both the region merging schemes are based on the watershed depth of regions and serve to reduce the over …

Modeling And Analysis Of Social Networks, Robert S. Renfro Ii

Theses and Dissertations

This dissertation develops new methods for the modeling and analysis of social networks. Social networks describe the complex relationships of individuals and groups in multiple overlapping contexts. Influence in a social network impacts behavior and decision making in every setting in which individuals participate. This study defines a methodology for modeling and analyzing this complex behavior using a Flow-Model representation. Multiple objectives in an influencing effort targeted at a social network are modeled using Goal Programming. Value Focused Thinking is applied to model influence and predict decisions based on the reaction of the psychological state of individuals to environmental stimuli. …

Metallurgical Evaluation Of Cast Duplex Stainless Steels And Their Weldments, Songqing Wen

Masters Theses

Duplex stainless steels (DSS) are being specified for chloride containing environments due to their enhanced pitting and stress corrosion cracking resistance. They exhibit improved corrosion performance over the austenitic stainless steels. Duplex stainless steels also offer improved strength properties and are available in various wrought and cast forms.

Selected grades of duplex stainless steel castings and their welds, in comparison with their wrought counterparts, were evaluated, regarding corrosion performance and mechanical properties and weldability. Multiple heats of cast duplex stainless steel were evaluated in the as-cast, solution annealed (SA) static cast and SA centrifugal cast conditions, while their wrought counterparts …

Lateral Migration Of A Solid Particle In Shear Flow, Wutthapong Jiraporncharoen

Masters Theses

Lateral migration of solid particles in shear flow is observed in various industrial applications. Suspensions in a blade coater, a device used to apply coating pigment to a base paper to improve paper properties, is an example. Particle hydrodynamics will affect the quality of coated paper and runnability of the coater especially when the speed of the coating machine is very high or the pigment concentration is increased.

Many factors will affect the particle migration. The wall repulsion or lubrication effect forces the particle away from a wall to the channel center. The inertial effects are increased by increasing the …

Electrical Activation Studies Of Ion Implanted Gallium Nitride, James A. Fellows

Theses and Dissertations

A comprehensive and systematic electrical activation study of Si-implanted GaN was performed as a function of ion implantation dose, anneal temperature, and implantation temperature. Additionally, Mg-implanted GaN was also investigated. Temperature-dependent Hall effect measurements and photoluminescence (PL) spectra were used to characterize the samples. GaN wafers capped with AlN were implanted with Si ions at doses ranging from 1x10¹³ to 5x10¹⁵ cm^-2 and annealed from 1050 to 1350 °C. The optimum anneal temperature for samples implanted with the higher Si doses is around 1350 °C, exhibiting nearly 100% electrical activation efficiency. Exceptional mobilities and carrier concentrations were …

Modeling Axisymmetric Optical Precision Piezoelectric Membranes, James W. Rogers Jr.

Theses and Dissertations

The US Department of Defense (DOD), as well as the National Aeronautics and Astronautics Administration (NASA) and the Jet Propulsion Laboratory (JPL) are interested in developing and deploying precise, compliant, light-weight, space-based structures. More specifically, the Air Force’s core competencies ‘Aerospace Superiority’ and ‘Information Superiority’ demand ever-increasing depth and breadth of capability. Whether used for energy transmission or optical reconnaissance, current launch restraints limit rigid space-based optical reflector size. To support this requirement, the Air Force Research Laboratory (AFRL) is developing a large space-based optical membrane telescope. Inflatable reflectors can conceptually break this barrier, but controlling such a compliant structure …

Low Proof Load Prediction Of Ultimate Strengths Of Fiberglass/Epoxy I-Beams Using Acoustic Emission, Edward C. Fatzinger Jr.

Master's Theses - Daytona Beach

Acoustic emission (AE) nondestructive testing was used to monitor fiberglass/epoxy I-beams. The experiment consisted of loading the I-beams in cantilever fashion with a hydraulic ram. While testing, AE waveforms were collected from the onset of loading to failure. After acquisition, the AE data from each test were filtered to include only data collected up to 50% of the theoretical ultimate load for further analysis.

A Kohonen self-organizing map was utilized to separate each individual data point (hit) into failure mechanism clusters. Then a multiple linear regression analysis was performed using the percentage of hits associated with each failure mechanism along …

Design And Construction Of A 1/3-Scale, 1986 Cessna 172p Flight-Test Aircraft, Michael J. Hinton

Master's Theses - Daytona Beach

The incredible cost of prototype flight testing can be a very limiting factor in the optimization of new designs as they proceed from the drawing board to the flight line. The use of low-cost scaled models to predict full-scale prototype performance is the focus of this project. It will be shown that by strictly following geometric and dynamic scaling criteria, the scaled aircraft's flight performance can be predictably related to the full-scale aircraft's performance. Many companies have performed scaled flight-testing of Remotely Piloted Vehicles (RPV's) and there is much speculation as to the results of these tests, but non-proprietary information …

The Effect Of Cockpit Noise On Aircraft Pilot Psychomotor Performance, Kelechi (Kc) Nwabeke

Master's Theses - Daytona Beach

The purpose of this study was to evaluate the effect of cockpit noise on aircraft pilot psychomotor performance on a simulated tracking task. The performance of thirty-two participants was measured on a vertical and horizontal tracking task. In the control group, eight participants were used in a quiet condition. In the experimental group, eight participants were exposed to low intensity cockpit noise (50 dBA), eight participants were exposed to medium intensity cockpit noise (60 dBA) and eight participants were expose to high intensity cockpit noise (70 dBA). The performance of the control and experimental groups was measured in an advanced …

Automated Myocardial Infarction Diagnosis From Ecg, Chen Zhou

Doctoral Dissertations

In the present dissertation, an automated neural network-based ECG diagnosing system was designed to detect the presence of myocardial infarction based on the hypothesis that an artificial neural network-based ECG interpretation system may improve the clinical myocardial infarction. 137 patients were included. Among them 122 had myocardial infarction, but the remaining 15 were normal. The sensitivity and the specificity of present system were 92.2% and 50.7% respectively. The sensitivity was consistent with relevant research. The relatively low specificity results from the rippling of the low pass filtering. We can conclude that neural network-based system is a promising aid for the …

Techniques For Reduced Order Modeling Of Aeroelastic Structures With Deforming Grids, John S. R. Anttonen

Theses and Dissertations

Reduced order modeling (ROM) seeks to make the modeling of aeroelastic behavior practical by reducing computation time for design codes. Deforming grids are often used in aeroelastic problems to account for the deformation of the structure. Proper Orthogonal Decomposition (POD/ROM) is a ROM technique that operates in an index-space for computations, not accounting for changes in grid dynamics, and must be modified to reflect grid deformation properly. To investigate and account for the effects of grid deformation on POD/ROM, a new algorithm is developed that incorporates modifications to the usual formulation. Evaluation of the new algorithm is accomplished through application …

Determination Of The Impact Of A Human Capital Decision Cost Model On The Economic Performance Measures Of A Technical Services Company, Jeffery A. Temple

Engineering Management & Systems Engineering Theses & Dissertations

Human Capital has a major impact on cash flow management decisions in a Technical Services company. Decisions to hire or terminate employees to meet contract requirements affect the company's economic value. The objective of this research is to develop a model that assists management in establishing a starting point in making, as efficiently as possible, those decisions that impact employees' lives. To understand that impact, the operations and economic parameters of a Technical Services company are compared with those of a manufacturing company. This analysis establishes two · essential points for Technical Services organizations; first, that the capital investment decision …

A Decomposition Approach For The Multi-Modal, Resource-Constrained, Multi-Project Scheduling Problem With Generalized Precedence And Expediting Resources, Michael L. Fredley

Theses and Dissertations

The field of project scheduling has received a great deal of study for many years with a steady evolution of problem complexity and solution methodologies. As solution methodologies and technologies improve, increasingly complex, real-world problems are addressed, presenting researchers a continuing challenge to find ever more effective means for approaching project scheduling. This dissertation introduces a project scheduling problem which is applicable across a broad spectrum of real-world situations. The problem is based on the well-known Resource-Constrained Project Scheduling Problem, extended to include multiple modes, generalized precedence, and expediting resources. The problem is further extended to include multiple projects which …

Theater-Level Stochastic Air-To-Air Engagement Modeling Via Event Occurrence Networks Using Piecewise Polynomial Approximation, David R. Denhard

Theses and Dissertations

This dissertation investigates a stochastic network formulation termed an event occurrence network (EON). EONs are graphical representations of the superposition of several terminating counting processes. An EON arc represents the occurrence of an event from a group of (sequential) events before the occurrence of events from other event groupings. Events between groups occur independently, but events within a group occur sequentially. A set of arcs leaving a node is a set of competing events, which are probabilistically resolved by order relations. An important EON metric is the probability of being at a particular node or set of nodes at time …

Development Of An Integrated Photonic Sensor For Monitoring Hazardous Organics, Dianhong Luo

Dissertations

In this study, an integrated photonic sensor has been designed and fabricated for the purpose of monitoring hazardous organics in the environment. The operation of the sensor is based on the principles of the Mach-Zehnder interferometry. The sensor consists of a patterned waveguide structure made of phosphosilicate core and silica cladding. LPCVD processes were developed to produce undoped cladding and doped core silicon dioxide films. Diethylsilane (DES), Trimethylphosphite (TMP) and oxygen were used as the precursors for the deposition process. The effects of the O₂/DES ratio and deposition temperature on the properties Of SiO₂ films were investigated. …

Buckling Of Composite Conical Shells Under Combined Axial Compression, External Pressure, And Bending, Youngjin Chung

Dissertations

Conical shells are extensively used in space crafts, robots, shelters, domes, tanks, and in machinery or devices (e.g. as Belleville washers). Thus, the design of minimum weight, maximum strength, stiffened conical (and cylindrical) shells under combined loads has long been of interest to designers. The objective of this study is to improve the strength of conical shells and reduce the weight of the structure. Buckling of composite conical shells subjected to combined axial loading, external pressure, and bending is investigated using energy and finite element methods. The conical shells have single and multiple layers, different cone angle, length, and radius. …